A focus on advanced physico-chemical processes for olive mill wastewater treatment

Advanced chemical remediation strategies (advanced oxidation processes, AOPs) have turned out as a feasible solution for the treatment of bio-refractory effluents, as in the case of olive mill wastewater (OMW). In this review paper, a focus on the relevant state-of-the art on advanced physico-chemical processes - including ozonation, wet oxidation, Fenton's reagent, photocatalysis, coagulation-flocculation, as well as electrochemical, solar-driven and hybrid processes - for the treatment of OMW is presented. In particular, the extent of recalcitrant organic pollutants abatement efficiency and the grade of mineralization achieved by the various treatments available up to today is addressed. Special attention is given to the different configurations and treatment line sequences, some important effect parameters and novel materials for implementation at real industrial scale. The latter includes the latest advances and applications for OMW treatment with biopolymers for coagulation-flocculation, ferromagnetic nanocatalyst for ease of recovery and multiple long-term use, low-cost catalysts, doped nanocatalysts for enhanced sunlight activation, zeolite-based catalysts, mixed and doped electrodes, among others. Solutions reported for the management of the secondary sludge by-produced in some treatment processes are also discussed. Moreover, a glance at the specific energy consumption and associated costs comparison of the different processes proposed is also given.